Date Approved

2016

Date Posted

4-27-2016

Degree Type

Open Access Senior Honors Thesis

Department

Biology

First Advisor

Dr. Jamie Cornelius

Second Advisor

Dr. Kristin Judd

Abstract

Migrants may employ different strategies that best optimize energetic trade-offs/ costs associated with specific metabolic demands in preparation for and during their seasonal movements. One strategy is known as partial migration, where members of the same population exhibit either migratory or sedentary behavior patterns. The American goldfinch (Spinus tristis), a known partial migratory species, displays a latitudinal distribution of age-sex classes across the winter range during their migratory phase. Females and adult males migrate further south than juvenile males to overwinter. The purpose of this study was to determine whether corticosterone (CORT), a hormone related to high-energy costs or activity, might explain this migratory behavior. Increases in CORT have been found in several seasonal migrants and may support associated physiological and behavioral changes during this life-history stage. We measured basal and stress induced CORT levels among age and sex classes influencing migratory status. Samples were extracted during late-breeding and migratory phase. A general linear model determined predictor variables that induced basal and stress-induced CORT levels. Body condition was the only significant variable negatively correlated with stress-induced CORT levels (p = 0.03). In addition we observed a significant negative relationship between body mot intensity and stress responsiveness in Goldfinches (p = 0.05). Our findings add to our understanding of how glucocorticoids support seasonal life history stages comparing the different CORT levels across age and sex classes.

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